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GU LECTURE  Hydration is important
 May aggravate renal failure
Kidney Ureter Bladder : KUB
 KUB is variously called as plain film or scout
film. It is done preliminary to IVP.
 Difference in x-ray attenuation between the
kidneys and the enveloping perirenal fat in
plain films provides a crude index of renal
anatomy and pathologic changes Retrograde Pyelogram
 Preliminary to IVP  Like IVP, retrograde pyelography relies on
 Since IV contrast can hide the calculi (same x- contrast medium to produce detailed X-ray
ray density as contrast) it serves as the film of images of the urinary tract.
reference for all subsequent films done after Utility
injection of contrast material.  Defines ureters and collecting systems
 Good to pick up calcifications. Observe for  While newer diagnostic techniques have
calcification over kidney, ureters, bladder replaced this test for many functions,
regions and rest of the abdomen retrograde pyelography may still yield better
 Can identify distended bladder definition of the upper urinary tract,
particularly the ureter and kidney collecting
 Can identify abdominal and pelvic masses.
syst
Observe renal outline for size and mass
Indications
density.
 Commonly performed when IVP produces an
 Incidental non diagnostic findings on KUB may
inadequate picture. Useful to study urinary
alert the physician to the possibility of urinary
tract obstruction when further clarification of
tract injury
nature of ureteral obstruction is required
 In trauma fracture of vertebrae, ribs or pelvis
 It also complements cystoscopy while
alerts you to GU tract injury.
investigating a patient with hematuria or
 Psoas obliteration and concavity of spine recurrent or suspected cancer.
towards the side of pathology.
 Detects small lesions in the collecting system
 Abnormal air collections suggestive of renal or E.g. Transitional cell carcinoma
peri-renal abscess Limitations
 Contrast complications
Intravenous Pyelogram (IVP)
 May aggravate an existing urinary tract
 IVP is a radiological test that uses contrast to
infection or triggering one from the
outline the kidneys, ureters and bladder.
catheterization.
 Also known as intravenous urogram
Utility Voiding cystourethrogram (VCUG)
 Useful for evaluating the anatomy of the  Children with urinary tract infections.
kidneys, ureters and bladder
 One can detect function when no contrast is  Reflux is detected if contrast is seen to
excreted flow in retrograde fashion up the
 absence of renal function . ureters from the bladder.
 absence of perfusion to a kidney  Pelvic trauma where rupture of the bladder or
urethra is suspected.
 Useful to identify urinary tract obstruction
 Useful to evaluate reno-vascular disease  If the bladder is ruptured,
Common indications extravasation of contrast will be seen
 Renal colic outside the bladder in the pelvis or
 Hematuria abdomen.
 Recurrent urinary tract Infections  If urethra is ruptured, there is
 Suspected reno-vascular hypertension extravasation into the perineum
Disadvantages  Patients with suspected bladder outlet
 Labor and time intensive – it may take up to 6 obstruction
hours to complete in the severe obstruction  Obstructions or strictures or injury of
 It requires placement of an intravenous line. the urethra can be seen on the x-rays
taken during voiding.
 Requires a bowel preparation for optimal
Limitations
results
 Insertion of the catheter is painful.
 Involves intravenous injection of potentially
allergic and mildly nephrotoxic contrast  While conventional voiding cystograms are still
necessary to evaluate the male urethra for
 Nonionic contrast agents have lowered the
posterior valves and bladder trauma, the
incidence of adverse reactions.
majority of reflux studies today are done
 IVP's are not useful in patients with renal
effectively with radionuclide cystography.
dysfunction.
 Newborns rarely have sufficient renal ULTRASOUND
concentrating ability to allow the kidneys to be
seen on an x-ray.
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 The use of high-frequency sound waves to  Most young children require sedation to
produce real-time images, provides a simple undergo a CAT scan.
and painless way to examine the kidney,  CAT scans are relatively expensive
bladder, prostate and scrotum
Advantages MRI
 Non-invasive test  MRI is as good as CT or better in characterizing
 Requires no preparation lesions of kidney and prostate.
 No pain  Because of its ability to show soft tissues in
 Provides accurate anatomic information, exquisite detail, MRI can detect disease and
including dimensions evaluate renal vasculature and inferior vena
 No radiation risk cava
 Avoiding the potential allergic and toxic  MRI can delineate a cyst from a solid mass.
complications of contrast media.  In can identify the spread of kidney cancer into
 Can be used on individuals with poor kidney the renal vein, inferior vena cava and perirenal
function in whom contrast cannot be given area (Staging).
 No complications Indication
 Can be done at bedside  When contrast CT cannot be done
 Relatively economical exam  MRI is useful to evaluate vascular lesions
Utility Disadvantages
 Helpful in defining renal, bladder and prostate  Expensive
anatomy  Limited availability
 MRI has limited applicability for the urinary
 It is the test of choice to exclude Urinary tract
tract since the non-specificity of its signals
obstruction
makes it ineffective in detecting calcifications
 US can, in the majority of cases, diagnose and bladder abnormalities.
hydronephrosis.
 Patients with pacemakers, aneurysm clips, ear
 Good for evaluating Kidney size implants and metallic pieces in vital body
 Good to distinguish between cysts and solid locations cannot be imaged safely
mass.
 Good to localize kidney for biopsy ADRENALS
Common indications Adrenal Adenoma
 Renal mass / Abdominal mass  Incidence in the population is 2-8%
 Renal colic  Diagnosis is often made as an incidental
 Recurrent Urinary tract infections finding on CT examination.
 Chronic renal failure  In patient with no known primary, an adrenal
 Acute glomerulonephritis mass is almost always a benign adenoma
 Hematuria  In a patient with a known neoplasm, especially
lung cancer, an adrenal mass is problematic
Renal CT and diagnosing a metastasis versus an
 CT scanning combines X-rays and computer to adenoma is critical for prognosis
produce precisely detailed cross-sectional CT findings
images of the genito urinary system.  Size greater than 4 cm tend to be metastases
 Utility or adrenal carcinoma
 A CT scan is helpful in delineating the  Heterogeneous appearance and
characteristics of anatomy and function irregular shape are malignant
of Kidneys characteristics
 Three-dimensional reconstructions of  Homogeneous and smooth are benign
the kidney and blood supply provide characteristics.
"road maps" for planning surgeries.  Intracellular lipid in adenoma results in
INDICATION low attenuation on CT
 Ultra fast CT is considered preferable to KUB  Little intracytoplasmic fat in metastases results
for detection of suspected stones in high attenuation on non-enhanced CT
 If ultrasound evaluation is equivocal for a cyst,  Non-enhanced CT (NECT)
or is suggestive of malignancy  Threshold 10 HU
 In evaluating solid abdominal masses  Sensitivity 79%, specificity 96%
 Hematuria  Contrast-enhanced CT (CECT)
 Local staging of cancer Kidney to allow  Because majority of CT examinations in
definitive surgical management if needed oncology use IV contrast, the %
 Renal artery and vein evaluation washout is useful after 10 minutes.
DISADVANTAGES  Adenomas have greater than 50%
 Requires placement of an intravenous line for washout after 10 minutes
IV contrast.  Washout can also be used on adrenal
 Exposes patient to radiation. masses that measure > 10 HU on NECT
 Contrast toxicity or allergy  Alternative is to do MR or PET
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 they are usually round or oval masses
Adrenocortical carcinoma with an attenuation similar to that of
 rare malignancy with a poor prognosis. the liver
 reported incidence: 2 cases per million  Larger lesions frequently demonstrate
persons. necrosis, hemorrhage, and fluid-fluid
 tumors frequently are large, measuring 4-10 levels.
cm in cross-sectional diameter.  As a result, they often appear
 arise from the adrenal cortex inhomogeneous.
 bilateral in up to 10% of patients.  Calcification is rare, but it is reported
 Approximately 50-80% are functional tumors,
with most causing Cushing syndrome. KIDNEYS
Endocrine syndromes associated with adrenocortical Acute Pyelonephritis
carcinoma Etiology
 Cushing syndrome o Inflammation of the renal parenchyma and
 Virilization and precocious puberty renal pelvis due to an infectious source
o Most often secondary to an ascending lower
 Feminization
urinary tract infection from gram-negative
 Primary hyperaldosteronism
bacteria
CT findings
E. coli
 Large mass (>4 cm) Klebsiella
 Central necrosis or hemorrhage Proteus
 Heterogeneous enhancement Pseudomonas.
 Invasion into adjacent structures o Exception is S. aureus, which is spread
 Venous extension into the renal vein or inferior hematogenously
vena cava Pathologic Causes
o Vesicoureteral reflux
Adrenal metastases o Obstruction in the collecting system usually
 Unilateral adrenal mass or enlargement due to a calculus
Small masses (<1 cm) - Adenoma, Complications
ganglioneuroma, hyperplasia, metastasis, and o Abscess
pheochromocytoma o Emphysematous pyelonephritis
Large masses (>4 cm) - Carcinoma of Most often occurs in diabetics
adrenal cortex; cyst or pseudocyst; hematoma; Can produce gas in the collecting
infection; inflammation (eg, tuberculosis, system and renal parenchyma.
histoplasmosis); metastasis (eg, lung or breast Radiographic Imaging Findings
related); myelolipoma; neuroblastoma, o Enlarged kidneys (U/S and CT)
ganglioneuroblastoma, or ganglioneuroma; o Hydronephrosis (U/S and CT)
pheochromocytoma (eg, multiple endocrine o Wedge shaped areas of low attenuation
neoplasia) secondary to decreased perfusion (CT)
o Loss of the ability to distinguish the
 Bilateral adrenal enlargement
corticomedullary border (CT)
Common causes - Hemorrhage (eg, in infants,
o Perinephric stranding (CT)
trauma, bleeding disorder), histoplasmosis,
hyperplasia, metastasis (eg, lung or breast
Emphysematous Pyelonephritis
related), neuroblastoma, and tuberculosis
Acute, fulminant, necrotizing infection of kidney and
Uncommon causes - Addison disease,
perirenal tissues associated with gas formation which
adenomas, amyloidosis, carcinomas (eg,
may be life-threatening
multiple, primary), infection (ie, others),
lymphoma, pheochromocytoma (multiple • Organism
endocrine neoplasia), and Wolman disease (eg, o E. coli (vast majority of cases)
familial xanthomatosis) o Klebsiella pneumoniae (9%)
CT findings o Proteus mirabilis
 appear as focal masses or distortion of the o Pseudomonas
contour of the adrenal gland. o Enterobacter
 smaller than 3 cm may be homogeneous. o Candida
 Larger lesions may have central necrosis or o Clostridia (exceptionally rare)
hemorrhage. These lesions are heterogeneous • Location
and may have thick enhancing rims. They may o Most are unilateral
also invade contiguous organs such as the
o 5-7% bilateral
kidneys.
 Attenuation values of less than 10 HU on • Types
unenhanced o Type I (33%)
• Streaky or mottled gas in
Pheochromocytomas interstitium of renal
 CT parenchyma radiating from
 large tumors (often >3 cm), medulla to cortex
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• Crescent of subcapsular or  Traumatic avulsion of renal
perinephric gas artery
• No fluid collection (= no  Surgery
effective immune response) o Embolism
• Prognosis in this type is poor  Cardiac origin
(69% mortality) • Rheumatic heart
• disease with
o Type II (66%) arrhythmia
• Bubbly and/or loculated o Atrial fibrillation
intrarenal gas (infers presence • Myocardial infarction
of abscess) • Prosthetic valves
• Renal and/or perirenal fluid • Myocardial trauma
collection • Left atrial or mural
• Gas within collecting system in thrombus
almost all • Myocardial tumors
• CT findings • Subacute bacterial
o Most reliable and sensitive modality endocarditis
o Mottled areas of low attenuation •
extending radially along the pyramids
o Extensive involvement of kidney and  Catheters
perinephric space • Angiographic catheter
o Air extending through Gerota’s fascia manipulation
into retroperitoneal space • Umbilical artery
o Occasionally gas in renal veins catheter above level of
• Ultrasound findings renal arteries
o High-amplitude echoes within renal o Arterial thrombosis
sinus and/or renal parenchyma  Arteriosclerosis
associated with "dirty" shadowing  Thrombangitis obliterans
• "Comet tail" reverberations  Polyarteritis nodosa
o Kidney may be completely obscured by  Syphilitic cardiovascular
large amount of gas in perinephric disease
space (DDx: surrounding bowel gas)  Aneurysms of the aorta or renal
o Gas may be confused with renal calculi artery
 Sickle cell disease
Renal Infarction o Sudden complete renal vein thrombosis
• Thrombotic disease usually affects larger o
vessels
• Lobar Renal Infarction
o Includes main renal artery
o Early signs
o Patients with thrombotic disease
usually present with hypertension or  Focal attenuation of collecting
renal insufficiency system
o Usually results from atherosclerosis • Tissue swelling
 But, blunt abdominal trauma  Focally absent nephrogram
may cause intimal tears with • Triangular with base at
subsequent dissection and cortex
thrombosis o Late signs
• Emboli can affect vessels of various sizes  Normal or small kidney(s)
depending on the size of the emboli  Focally atrophied parenchyma
o Renal artery emboli usually come from with normal interpapillary line
cardiac source  Cortical atrophy and irregular
o Embolic disease usually produces acute scarring are seen as late
symptoms sequelae
 Sudden onset of flank pain o CT
 Hematuria  Subtle renal infarcts are best
 Proteinuria demonstrated on CT
 Fever  Appear as wedge-shaped,
 Leukocytosis cortically based, hypodense
 areas
• Causes • Triangular in shape with
o Trauma widest part at the
cortex (base of infarct)
 Blunt abdominal trauma
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 Non-perfused area  Much more common in
corresponding to vascular females
division o Angiomyolipoma associated with
 Renal swelling may also be tuberous sclerosis (in 20%)
seen  Angiomyolipoma occurs in 80%
 Cortical rim sign of patients with tuberous
• Entire kidney is sclerosis
nonenhancing except • Commonly large
for the outer 24 mm of • Usually bilateral
cortex, which are • Usually multiple
perfused by capsular
branches
 May be only evidence of
tuberous sclerosis
 Mean age of incidence: teens
 Equal incidence in males and
females
o US • Imaging findings
 Focally increased echogenicity o Mostly small lesions <5 cm in diameter
 Color flow Doppler aids in diagnosis of o Many have a large exophytic
renal artery thrombosis component (25%)
• There is absence of an o Calcifications not common (6%)
intrarenal arterial signal o Plain film findings
• Tardus parvus waveform is  Mass of fat lucency is lesion is
seen if incomplete occlusion or large enough
collateral supply o CT findings
 Nuclear medicine  Well-marginated, cortical-
• Nuclear imaging shows a based, heterogeneous tumor
photopenic area corresponding predominantly of fat density
to the region of ischemia or (<-20 HU)
infarction  Variable enhancement (smooth
• Chronic Renal Infarction muscle, vessels)
o Pathology • US findings
o Highly echogenic tumor due to high fat
 All elements of kidney
atrophied with replacement by content
interstitial fibrosis o Less echogenic areas due to
hemorrhage, necrosis, dilated calyces
 Normal or small kidney with
smooth contour
Kidney, Trauma Grading
 Globally atrophied parenchyma • Grade 1
 Diminished or absent contrast o Hematuria with normal imaging studies
material density
o Contusions
o US
o Nonexpanding subcapsular hematomas
 Increased echogenicity (by 17
• Grade 2
days)
o Nonexpanding perinephric hematomas
Angiomyolipoma confined to the retroperitoneum
o Superficial cortical lacerations less than
• Benign mesenchymal tumor of kidney
1 cm in depth without collecting
• Rare system injury
• Histopathology • Grade 3 - Renal lacerations greater than 1 cm
o No true capsule in depth that do not involve the collecting
o Commonly bleed system
o Tumor composed of fat, smooth • Grade 4
muscle, aggregates of thick-walled o Renal lacerations extending through
blood vessels the kidney into the collecting system
• Types o Injuries involving the main renal artery
o Isolated angiomyolipoma is most or vein with contained hemorrhage
common (80%) o Segmental infarctions without
 Usually solitary associated lacerations
 Unilateral (80% on right side) o Expanding subcapsular hematomas
 Not associated with tuberous compressing the kidney
sclerosis • Grade 5
 Mean age of incidence: 40s o Shattered or devascularized kidney
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o Ureteropelvic avulsions • Hydronephrosis (83% sensitive, 94% specific)
o Complete laceration or thrombus of the • Perinephric fluid (82% sensitive, 93% specific)
main renal artery or vein
• Ureteral dilatation (90% sensitive, 93%
specific)
Nephrolithiasis/Urolithiasis • Soft-tissue rim sign (good positive predictive
• Passage of a urinary stone is the most common value with a positive odds ratio of 31:1)
cause of acute ureteral obstruction
KUB
-Conventional radiography is often performed as a ULTRASOUND
preliminary examination in patients with abdominal - on sonograms, stones are demonstrated as bright
pain possibly resulting from urinary calculi echogenic foci with posterior acoustic shadowing.
- Stones are visualized fairly well with US in the kidneys
and the distal ureter at or near the UVJ, especially if
• Stones are often found at key points of dilatation is present.
narrowing such as the UPJ, the ureterovesical - US is good for the visualization of complications such
junction (UVJ), and the point at which the as hydronephrosis (or other signs of obstruction);
ureter crossing the iliac vessels. An addition however, some patients with acute obstruction have
site is on the right side where the ureter passes little or no dilation.
through the root of the mesentery.
• Calcium stones as small as 1-2 mm can be
seen. Cystine stones as small as 3-4 mm may
be depicted, but uric acid stones are usually
not seen unless they have become calcified. Acute obstructive uropathy
- is a commonly encountered condition, occurring in
both inpatient and outpatient settings.
- The most common cause for acute obstructive
IVP
uropathy is an impacted calculus. In 70% of patients,
- useful for confirming the exact location of a stone
the level of obstruction is at the ureterovesical
within the urinary tract. IVU depicts anatomic
junction; in the remainder of patients, the ureteropelvic
abnormalities such as dilated calyces, calyceal
junction or mid ureter are the points where calculi tend
diverticula, duplication, UPJ obstruction, retrocaval
to lodge.
ureter, and others that may predispose patients to
- Most calculi (90%) contain calcium, combined with
stone formation or alter therapy
oxalate and/or phosphate.
- When a stone causes acute obstruction, an
- Magnesium ammonium phosphate (struvite) stones
obstructive nephrogram may be present. This may be
are the next most common type, and are observed
prolonged and hyperopaque, with increasing opacity
most frequently laminated with calcium apatite. They
over time. The nephrogram of acute obstruction is
form in the alkaline environment created by urease-
usually homogeneous, but may also be striated or
splitting bacteria, especially Proteus species, and
occasionally not visible on radiographs.
commonly produce the staghorn appearance of the
- Other signs include delayed excretion, dilatation to
pelvocalyceal system.
the point of obstruction, or blunting of the calyceal
- Uric acid stones are less common, These stones,
fornices. Immediately after the passage of a stone,
along with the less common xanthine and matrix
residual mild obstruction or edema can be detected at
calculi, appear radiolucent on plain radiographs.
the UVJ. Delayed images may be needed to opacify to
Cystine stones are less opaque than calcium stones
the point of the obstruction, but using gravity to
and may be difficult to demonstrate on plain
position the more opaque and more distal contrast
radiographs.
material–laden-urine is also possible by placing the
patient in a prone or erect position.
IMAGING
CT SCAN
CT SCAN
- Unenhanced helical CT has both a high sensitivity of
-With a sensitivity of 94-97% and a specificity of 96-
95-98% and a high specificity of 96-100% in detecting
100%,
ureteral calculi in the acute setting. Both calcified and
- helical CT is the most sensitive radiologic examination
noncalcified calculi may be identified, along with the
for the detection, localization, and characterization of
location and size of the stone.
urinary calcifications
- Secondary signs of obstructive uropathy, including
- CT scans frequently depict non-obstructing stones
hydronephrosis, perinephric and periureteral stranding,
that are missed on IVU.
as well as ureterectasis, are well demonstrated on CT.
- CT is faster and no contrast agent is needed in most
patients.
ULTRASOUND
- CT easily differentiates between non-opaque stones
In the evaluation of acute flank pain, ultrasound (US) is
and blood clots or tumors (compared with IVU, which
limited primarily to pregnant patients. While US
may depict only a filling defect).
demonstrates renal calculi, it is poor at detecting
- helical CT is better than US or IVU in detecting other
ureteral stones
causes of abdominal pain
CT may depict the following:
• Stones in the ureter The hallmark of obstruction on US is the presence of
hydronephrosis. Prominent anechoic structures within
• Enlarged kidneys
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the renal sinus represent a dilated pelvocalyceal Intravenous urography
system. Renal calculi also may be demonstrated as Intravenous urography (IVU) is also limited in depicting
echogenic foci with or without shadowing. This finding RCCs. Large lesions, which can distort the renal contour
depends on the size of the calculi, with smaller stones or the collecting system, may be detected.
blending into the echogenic renal sinus. Ureteral calculi Findings of RCC are nonspecific and include
and ureterectasis are detected less often. While UPJ - mass effect on the collecting system,
and UVJ stones may be observed, mid ureteral stones - distortion of the renal contour,
are extremely difficult to detect. - enlargement of a portion of the kidney, and
- calcifications.
KUB - most RCCs are less attenuating than surrounding
The plain abdominal radiograph or KUB film has long renal parenchyma.
been the initial imaging study of choice in patients - Renal vein invasion may be inferred if contrast
presenting with symptoms of acute flank pain material excretion by the affected kidney is poor or
absent. Alternatively, this finding may result from
extensive involvement of the kidney or ureteral
While 90% of stones contain calcium, the sensitivity of obstruction caused by mass effect.
plain films has been reported at only 50-60%, with a
specificity of 70%. CT SCAN
- On initial nonenhanced CT scans, RCCs may appear
Most noncalcified stones, blood clots, and most other as isoattenuation, hypoattenuation, or
intraluminal obstructive causes are radiolucent; hyperattenuation relative to the remainder of the
therefore, they are not seen on abdominal radiographs. kidney. Calcifications may be present and are usually
In trauma, the presence of pelvic fractures and soft amorphous and internal, although rimlike calcifications
tissue mass in the abdomen or pelvis may alert the can also be present.
radiologist to the possibility of ureteral injury, a rare - On contrast-enhanced CT scans, RCC is usually solid,
complication, or obstruction from a large hematoma. and evidence of necrosis is often present. Sometimes
RCC is a predominantly cystic mass, with thick septa
and wall nodularity.
RCC may also appear as a completely solid and highly
enhancing mass.
Renal Cell Carcinoma - Staging of RCC, which can be performed by using CT
- the most common primary renal malignant neoplasm or MRI, includes the assessment of ipsilateral or
in the adult. contralateral adrenal involvement, direct extension into
- It accounts for approximately 85% of renal tumors adjacent organs, enlargement of retroperitoneal lymph
and 2% of all adult malignancies. nodes, invasion of the ipsilateral renal vein (with or
- RCC is more common in men than in women (ratio, without extension into the inferior vena cava), and
2:1), and distant metastatic disease (liver, bone, lungs).
- it most often occurs in patients aged 50-70 years. Retrocrural, subcarinal, or mediastinal lymph nodes
can also be enlarged.
RCCs can be staged by using the American Joint ULTRASOUND:
Committee on Cancer TNM classification, as follows: On sonograms, RCC can be isoechoic, hypoechoic, or
hyperechoic relative to the remainder of the renal
• Stage 1 RCCs are 7 cm or smaller and confined parenchyma. - Smaller lesions with less necrosis are
to the kidney. more likely to be hyperechoic.
• Stage 2 RCCs are larger than 7 cm but still - Isoechoic tumors are detected only by distortion of
the renal contour, focal enlargement of a portion of the
organ confined.
kidney, or distortion of the central sinus fat.
• Stage 3 tumors extend into the renal vein or - For the workup in RCC, US is used primarily to
vena cava, involve the ipsilateral adrenal gland differentiate solid masses from simple cysts and to
and/or perinephric fat, or have spread to one visualize the internal architecture of lesions more
local lymph node. effectively than can be accomplished by using CT or
• Stage 4 tumors extend beyond the Gerota MRI.
fascia, to more than one local node or have
distant metastases URINARY BLADDER
Bladder cystitis
Findings: - is defined as inflammation of the urinary bladder
Plain radiography from any cause.
Plain radiographic findings are often unrevealing in -female individuals, especially those younger than 50
patients with RCC unless the mass contains detectable years, are affected more often than male individuals
calcification or is large enough to distort the normal -. The high incidence in women is due to the short
renal contour. Plain radiography has no role in the length of the urethra and its proximity to the anus.
primary search for RCC or in the follow-up observation
of patients with RCC because of its limited sensitivity ULTRASOUND:
and specificity. - The bladder appears sonographically normal in most
cases but may show thickening of its wall due to
edema.
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- The bladder mucosa is normally less than 2 mm thick
when measured at full distension and less than 5 mm
thick when nondistended.